Ink for Ceramic Surfaces

Abstract

The present invention concerns ink for printing on ceramic surfaces such as glass, which contains glass frits for silica nanoparticles and optionally a pigment, and is suitable for ink jet printing.

Description

FIELD OF THE INVENTION[0001]The present invention concerns ink for printing on ceramic surfaces, especially glass, subsequent to printing the surface undergoes calcining (firing) at temperatures above 600° C.BACKGROUND OF THE INVENTION[0002]Ceramic materials are hard, brittle, heat- and corrosion-resistant substrates made by shaping and then heating a non-metallic mineral, such as clay, at a high temperature. Enamels, porcelain, and bricks are examples of materials that are produced by molding or shaping minerals and baking or firing them at high temperatures.[0003]Glass products are typically made by fusing silicates with boric oxide, aluminum oxide, or phosphorus pentoxide at high temperatures. They have highly variable mechanical and optical properties and solidify from the molten state without crystallization into a transparent or translucent form. While glass items are generally hard and brittle, their lack of crystalline structure puts them in the class of amorphous solids. Gl...

AI Technical Summary

Benefits of technology

[0024]The composition above lacks pigments and thus is not intended to provided a colored printed pattern, Rather the “substrate forming binding composition” (see bellow) which is typically glass frit or silica nano-particles is printed for producing a “non colored pattern” for example to provide the glass with a rough, pattern, an opaque “matt” pattern sometimes desired for aesthetic or functional purposes on glass (such as for avoiding accidental collision of passengers into glass doors).

[0039]Integration of the pigment-less ink into a surface to provide a non-colored pattern may be used especially in architecture to provide rough, opaque or “matt” patterns or surfaces on windows or glass doors both for aesthetic purposes and for avoiding accidental collisions.

[0045]Where the ink also comprises pigment particles for providing a colored pattern the ink should maintain its optical properties after exposure to temperatures of above 500°, preferably after exposures to temperatures above 580°, most preferably after exposure to temperature of above 600°. The “optical properties” it should maintain are selected from color, optical density, UV blockage, gloss, etc. This means that the pigments used according to these embodiments do no loss their optical properties upon firing.

[0063]The solvent based ink may further comprise at least one UV-curable agent. Many times it is desired to fix the ink to the substrate, before the firing so as to improve the printing properties. Addition of UV curable agents enables rapid fixation of the printed pattern by exposing the surface-bearing ink droplets to UV radiation, after printing. Since the UV curable agents are organic molecules, they are burnt out during the firing of the printed glass pattern.

Problems solved by technology

While glass items are generally hard and brittle, their lack of crystalline structure puts them in the class of amorphous solids.

Thermoplastic ink systems are waxy at room temperature and have to be heated up for printing.

Controlling current flow is critical because too much will overheat the color and burn out the mesh.

While printing on ceramic surfaces with organic inks may be obtained by silk-screen, pad printing or digital printing, commercial ceramic inks are difficult to use in inkjet printing as they have typically a viscosity higher than required for inkjet printing (about 20-40 cps) and the glass frit contained in them, which is in the micron size range, tends to sediment and also clog the nozzles on the orifice plate from which the ink is jetted during inkjet printing.

Attempts at printing ceramics colors by the inkjet process and hence making the inkjet process available also for decorating ceramic articles, such as glass, enamel and porcelain, have hitherto always failed owing to the pronounced tendency of the specifically heavy and coarse color powders to form sediment.

Such suspensions would rapidly lead to blocking of the printing nozzles and of the entire inkjet printing apparatus.

Liquid color pastes having a substantially higher viscosity, for example 5000 mPa·s, such as are used in screen printing for decorating glass, will not be suitable for printing by ink jet, since the viscosity is much too high for the ink jet printers present nowadays.

Ink which is solid at room temperatures and has to be heated at the inkjet head prior to printing is awkward to handle, load, and requires special equipment for actual printing.

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